PORT OF SPAIN — President Barack Obama defended on Sunday his amicable first encounter with Venezuelan leader and anti-US firebrand Hugo Chavez, which critics back home assailed as naiive and "irresponsible".

"It's unlikely that as a consequence of me shaking hands or having a polite conversation with Mr. Chavez that we are endangering the strategic interest of the United States," Obama told reporters at the close of a Summit of the Americas.

But, he stressed he still had concerns about Venezuela and Chavez's often heated rhetoric.

"I have great differences with Hugo Chavez on matters of economic policy and matters of foreign policy," Obama said.

"There have been instances in which we've seen Venezuela interfere with some of the countries that surround Venezuela in ways that I think are a source of concern," he added.

Obama and Chavez met here Friday at the opening of a 34-nation Americas summit and photos of the encounter showed the US leader smiling as he shook the Venezuelan's hand and patted him on the shoulder.